I can tell you that I was in vegan heaven when we went to Maui earlier this year. If you go there, definitely head to Paia on the north shore and eat at Veg Out (yummy vegan and some vegetarian stuff) and also Fresh Mint (a delicious all vegan thai place). Also in Paia is Mana Foods, a great vegan friendly grocery store. And the Flatbread Pizza Co. there is also really good and they can do yummy vegan pizzas.

Not sure what equals fun in your book, but other than food, there is lots of great hiking, whale watching peak is more in winter (February was awesome this year for watching whales), and Baldwin beach in Paia was a great, less touristy chill place to enjoy the ocean. Also if you snorkel and scuba dive it's great on Maui and when the whales are around you can hear them singing when you're under water!

We stayed at the Maui Retreat and it was amazing if you are looking for a place on the north shore (this is not the West or South Maui where most of the tourists are). It's a very eco-friendly place to stay (like, you can't even flush your toilet paper!) and the owners are very much hippie-ish so you would want to be up for that part.

The Big Island doesn't have any all vegan places but there are great health food stores and delicious omni restaurants. But all that really matters when you're in Hawaii is the awesome fruits and vegetables. If you aren't having a pineapple a day you aren't doing it right.

Hiking is top of my list. The botanical gardens, Volcano Park, nature stuff.

I'm ok with hippies in small doses. Well, not ok, but, you know. I mean, I was thinking about staying here for a few days, and it looks like I might get lice, accidentally join a sex cult, or be sacrificed to the Wicker Man (in that order of likelihood). On the other hand, free fruit.

Thanks for the recommendations! I'm slowly zeroing in on what I want to do while I'm there. Namely, eating a bunch of fruit.

Stay somewhere with a kitchen. You may want to bring or buy a good knife, since most rentals have shitty knives for cutting up the fruit. I suggest spending at least part of the time on the Hilo side -- it's closer to Volcano Nat'l Park and the viewing area (if it's still happening or open when you go), plus fewer tourists go there. I actually had more fun on that side and we rented a house, which rocked. Like someone else mentioned, there are tons of health food stores, not to mention the farmers' markets. And fruit stands. Holy shiitake, so much fruit. <3 <3 <3

The southern part of the island is also probably worth a day of exploring -- pretty sparsely populated but some really amazing things to see (and I think there is a small market in a town down there, but it wasn't on the day we drove through).

If you are into coffee, do a little research about the myriad coffee tours offered in the Kona growing area (well, there are some outside it, but they are chock-a-block up there). I found that most of the beans were ridiculously overroasted -- honestly, I didn't have a single great cup of coffee in Hawaii. The tour I went on was pretty boring, and the only thing I learned was that peaberry coffee is kind of a scam.

If you are into biking, which I am not but my boyfriend is, I can get you some notes about that. Well, he's into road biking -- and regretted not bringing his bike into Volcano -- but it seems like you could go more places with a mountain bike.

There are a zillion little corners and sights to see. Go, explore, enjoy! Just have a kitchen and get some basics and you'll be set for food. The restaurants weren't where it was at for us, anyway.